Implement the detection of USB Flash devices on IVI.

BUG=XWALK-2040

This patch implement the feature of detecting USB Flash devices on ivi, as well as getting its "capacity" and "isRemovable" attributes.
One more thing is the storage event, you could see there is a timeout in `storage_info_storage.cc`. This is alos because the historic reason, if use udev for all, then we should use the udev event instead of the timeout.